Slip lanes meeting at ~ 60-75º angle

[jakeroot]

In Australia, most new slip lanes meet the approach road (?) at about a 60-75 degree angle, so as to discourage people from forgetting their priority, or rather a lack thereof (so I can tell). I've compiled a short list of an intersection from each Australian state to prove that it is in fact an accepted engineering movement across the country:

QLD: http://goo.gl/b0NYfT
NSW: http://goo.gl/udS0Pm
WA: http://goo.gl/PYbVYK
NT: http://goo.gl/jPyMBk
VIC: http://goo.gl/8Kk1bN
SA: http://goo.gl/jBQlQd
(I've excluded Tasmania because I was only able to find a few slip lanes overall, and most were the old style).



In the US, however, I have only found one example, and it's where the Boulder Highway meets Lake Mead Parkway in Henderson, Nevada:

http://goo.gl/mpNwz7

Anybody else aware of intersections with slip lanes that meet in such a manner?... and not like this: http://goo.gl/wOlpbO (where they appear to simply merge).

I did find one diagram on ite.org that shows the tighter angled slip lanes having greater pedestrian visibility:

[realjd]

From what I remember from the last time I was there, those "slip lanes" were only used in cases where left on red was allowed.

[jakeroot]

From what I remember from the last time I was there, those "slip lanes" were only used in cases where left of red was allowed.

I can't say I'm sure what you mean when you say "left of red". Unless you meant "left ON red", in which case I am still not sure.

[DaBigE]

Unfortunately, aerial photos haven't been updated recently enough to show, but when slip lanes are involved in a reconstruction around here, they are being redesigned to intersect at a sharper angle. WisDOT even specifies this in the design of slip lanes (more commonly referred to as "partial right turn bypasses" around here) for roundabouts:

A partial bypass lane with a curbed vane island requires approaching vehicles to yield to traffic leaving the
adjacent exit. This alternative "˜snags' the right turner from making a through movement while preserving good
sight to the left for circulating/exiting traffic. Generally an intersection angle of 70 degrees or higher is desirable.
_{WisDOT FDM - Roundabout Design}

[realjd]

From what I remember from the last time I was there, those "slip lanes" were only used in cases where left of red was allowed.

I can't say I'm sure what you mean when you say "left of red". Unless you meant "left ON red", in which case I am still not sure.

I did mean to type "left on red". Left turns at a red light are illegal in Australia. In cases where they allow it, they often use a separate lane like that. Notice how they all have either a "turn left at any time with care" sign or a yield sign?

[Bitmapped]

The right turn movement from Boyers Avenue southbound onto US 19 NB/WV 7 WB in Star City, WV was reconstructed like this in conjunction with a new Sheetz. Current aerial photography is at http://goo.gl/maps/opgU0 .

I originally thought the change was because of the new RIRO turn lane to access Sheetz but perhaps not.  As part of the reconstruction, WVDOH changed this from a yield to a signalized movement.

[Mr_Northside]

The right turn movement from Boyers Avenue southbound onto US 19 NB/WV 7 WB in Star City, WV was reconstructed like this in conjunction with a new Sheetz. Current aerial photography is at http://goo.gl/maps/opgU0 .

I originally thought the change was because of the new RIRO turn lane to access Sheetz but perhaps not.  As part of the reconstruction, WVDOH changed this from a yield to a signalized movement.

Damn... that Sheetz is only ~1 mile from another Sheetz.  Between the interstate and the university, there's probably enough business to warrant both.  Man... it's been over 3 years now since I've been on that stretch of road.  Doesn't feel that long.

[jakeroot]

Posting back in this topic because I found something in the 1961 MUTCD (Chapter 4 on Islands) that, honestly, took my breath away. I have no idea where this photo was taken (or when, except obviously before the 1961 publishing), but the design of the right-turn bypasses (i.e. slip lanes or channelized right turns) at this intersection seem well ahead of their time.

The 70-degree meeting angle of slip lanes was something that I thought started in Australia/NZ, but apparently that's not the case?

[Scott5114]

Interesting. I didn't know the MUTCD used to include actual photographs instead of just diagrams.

(Also, you mean 75°. º is used as an ordinal indicator in other languages, like "st" or "th" in English.)

[jakeroot]

Resurrecting this topic again because I found the above image (finally). It's in Milwaukee, Wisconsin.

Of note, the intersection has been reconstructed a few times since the image. The bottom left slip lane was removed around 2000, but at some point between 1963-1995 a slip lane was added to the top left area (where the very old building once sat). Further, the slip lane in the bottom right has been converted into a right-only lane. Of further interest (to me, mainly), many other slip lanes in the nearby area have this 70-degree meeting angle, which as I said before, is not the typical meeting angle for slip lanes of that time. Given that this angle is now more or less desirable in high-ped areas, I can only assume that Milwaukee engineers were time lords and skipped ahead in time to discover this style of application.

I was concerned about the validity of my claim, but Historic Aerials suggests that I am correct in presuming this is the location.